Fabrication Of Copper-Containing Layers With High Wear Resistance And Their Antimicrobial Property

With relatively low price,good processability and antibacterial property,copper has wide application prospect in the fields of medical instruments and public health as a kind of metal-carrying inorganic antibacterial materials.However,the low hardness and poor wear-resisting performance become major constraint to its application.Therefore,under the premise of maintaining the antimicrobial ability,enhancement of hardness and wear-resisting property of copper has important implications.In this paper,rotationally accelerated shot peening and laser cladding technologies were used to prepare two kinds of antimicrobial copper lays with good wear-resisting property.First,gradient layer with nanostructure on pure copper was prepared by rotationally accelerated shot peening.The aim was to enhance the strength of copper and research the effect of surface nanocrystallization on wear-resisting and antimicrobial properties.In order to study the effect of the grain size on antibacterial performance of pure copper,we prepared ultra-fine grain copper material by equal channel angular pressing and nanocrystalline copper material by electroless plating.In addition,to increase the antimicrobial property of 304 stainless steel and promote its application in the fields of medical instruments and public health,Cu/Ti B₂ composite coating was producted on the surface of 304 stainless steel by laser cladding.And their antibacterial performance and wear-resisting property were evaluated.The main contents were as follows:1.The gradient layer with nanostructure was prepared by means of rotationally accelerated shot peening on pure copper.And the effect of procesing time on surface morphology,hardness,wear-resisting performance and antibacterial properties was studied.The results indicated that the hardness and wear-resisting property of shot peening specimens were significantly better compared with base metal.At the same time,the shot peening specimens performed better in the early stage of measurement of contact killing by wet plating.The roughness of the specimen after 15min-processing was lower than that after 5min-processing.Besides,the specimen after 15min-processing performed better in surface hardness,grain refinement（12nm）and wear-resisting property with smaller friction coefficient.2.In order to further investigate the effect of grain size on the antibacterial property of pure copper,the measurements of contact killing were taken on coarse grain copper,ultra-fine grain copper prepared by equal channel angular pressing and nanocrystalline copper prepared by electroless plating specimens.The results indicated that the nanocrystalline specimen showed more excellent antibacterial performance in the early stage.The sterilizing rate for E.coli was 62.4%after 15 min and for S.aureus was 81.4%after 60 min,being higher significantly than others.3.By means of study the effect of laser cladding parameters on morphology and microstructure of Cu/Ti B₂ composite coatings on the 304 stainless steel,the optimal laser parameters were obtained.On this basis,the surface morphology,hardness,wear-resisting performance and antibacterial property of coatings with different ingredients were compared.The results indicated that the coating with ingredient of 5wt.%（Ti+B）was preferred.It was observed that the composite coating exhibited a compact structure and achieved a firm metallurgical bond with the substrate without cracks and pores.Its surface hardness was more than twice that of coarse grain copper.In terms of wear-resisting performence,the composite coating showed a lower friction coefficient and a narrower wear scar,performing excellent wear resistance.In the antibacterial experiment,its antibacterial performance was generally close to that of coarse grain copper,which was outstanding compared with 304copper-containing stainless steel.4.In order to research the effect of copper ion concentration and bacterial suspension concentration on the antimicrobial performence of copper,the antibacterial experiments with different initial bacterial suspension concentration and different copper ion concentration were made.The results indicated that the effect of grain size on the antibacterial property of pure copper became more significant with the initial bacterial suspension concentration decreasing.And with the copper ion concentration increasing,the suppression function for E.coli became more obvious.5.The antimicrobial mechanism of copper was explored preliminarily by observed the morphology and internal structure of E.coli in contact with the copper surface.It was found that E.coli cells generally showed a concave state in the middle and there were a lot of cavities inside,while S.aureus retained more intact structure.